Luger Doubling

[JohnW...ski]

I have recently gotten my first Luger, an Interarms P08 with 6 in. barrel. I did consider an original Luger but wanted a 6" model that I could shoot without worry.

The Luger was bought through Gun Broker and came without a box but had 2 magazines. The condition is like new, in fact I doubt it had ever been fired, if it had it was very little.

The first times at the range were unremarkable, the pistol has a fairly heavy trigger pull that seems to have lightened a little after a few hundred rounds.

My problem is lately I get an occasional double, always when the next to last round in the magazine is fired then doubling the last round. It doesn't happen often maybe once or twice in a fifty round box loading 5 rounds per magazine. I have tried to reproduce the doubling loading 2 or 3 rounds in the magazine, but have never had it occur under those conditions. Like I said it only happens occasionally, yesterday I almost got through a box of 50 only to have it happen on the last two shots.

I have had the pistol apart, cleaned it, oiled it, with no difference. Inspection does not show anything unexpected, the sear looks fine, the plunger on the transfer bar is free, manually cycling the action while holding the trigger works normally.

Anyone have any suggestions?

Thanks,

John

[Lugerdoc]

John, Most likely your FP to sear overlap is too small or your flat sear spring is too weak. I would try replacing the spring first @$15 to see if that cures your problem. If not, I do have most other NOS Mauser Parabellum parts available. TH

[JohnW...ski]

Originally Posted by Lugerdoc

John, Most likely your FP to sear overlap is too small or your flat sear spring is too weak. I would try replacing the spring first @$15 to see if that cures your problem. If not, I do have most other NOS Mauser Parabellum parts available. TH

Thanks for the reply. I have just gotten back from the range after firing 100 rounds of Winchester 115 gr. FMJ ammo. Other
than a couple of stove pipes the pistol functioned flawlessly.

A friend gave me a couple of boxes of generic 9 mm. before I received the pistol and those were the first I had used in it also with no problems.

It appears the problem is with my reloads, cast bullet from a 122 gr. round nose Saeco mold over 3.5 gr Bullseye and a CCI small pistol primer. Not a hot load by any means but seems to have something to do with the problem.

John

[mrerick]

Also check to make sure that the little plunger on the front of the sear bar is properly lubricated and moving freely.

[JohnW...ski]

Originally Posted by rhuff

I would like to also mention that, at least for me, a Luger is easy to bump fire. I have had it happen with my Mauser Parabellum and a DWM P08. It happened when I had both Lugers at the range and using the same ammo(my reloads with 115gr FMJ and Unique powder)

I had been at the range for a fairly long session with both Lugers when it started to happen. I was loading 5 rounds, and the doubling occurred on #4 and #5 rounds. It made no difference as to what mags were used. Because it happened to both Lugers at the same session, I felt it had to be either my reloads or operator error.

I took both Lugers apart and examined them very closely, and found no problems with either. Long story short, I strongly believe that it was operator error of loosening my grip just enough near the end of the mag load and allowing bump firing to occur. I have taken both lugers to the range since then with no problems, and used the same batch of 9mm reloads the I used when the problem occurred.

I am just throwing this out for your consideration.

I appreciate the reply, I did consider the possibility of bump fire and still consider it a possibility but find it hard to believe when it has only happened with reloads and not once with 200 rounds of factory ammo. Also why only the 4 th. and 5 th. rounds?

I at least feel better after getting off 100 factory rounds without a problem.

John

[JohnW...ski]

Just got back from the range, fired 50 of my reloads, no doubling, no stovepipes, just normal operation.

Was going to take the Luger Docs advise and replace the sear spring but decided to give it a little more bend first. I removed the spring and measured the bow in the spring, it was .075", I then bent the spring in a vise until I had added .015" fora total bow of .090". Reassembled and checked the trigger pull, which I forgot to check first, it was 8 lbs.
Wish I could get that down to about 4 lbs. but satisfied for now.

Doesn't seem like there is a lot of leeway in how light the trigger pull of a Luger can be. Anyone know what is the normal range for trigger pull?

John

[John Sabato]

I had a luger once that had an extremely heavy pull which I attributed to the trigger return spring.

So I just set out to find a spring that was approximately the right winding diamter, and when I found one, in an odd ball point pen, I trimmed it to a reasonalble length, and used it behind the trigger, The result was a very satisfying 4.5 lb trigger...

It may take some experimentation, but I am sure anyone could do the same with any modification to the original gun parts.

[JohnW...ski]

Originally Posted by John Sabato

I had a luger once that had an extremely heavy pull which I attributed to the trigger return spring.

So I just set out to find a spring that was approximately the right winding diamter, and when I found one, in an odd ball point pen, I trimmed it to a reasonalble length, and used it behind the trigger, The result was a very satisfying 4.5 lb trigger...

It may take some experimentation, but I am sure anyone could do the same with any modification to the original gun parts.

The trigger alone requires ounces of force to pull on mine so the coil spring under would have little affect on the overall pull.

I honed the sear surfaces on both the firing pin and sear with an Arkansas stone, The trigger pull is down to 7-1/2 lbs. Another trip to the range and the pistol functioned flawlessly, so I guess I am on the right track. Still would like to take a couple more pounds of pull off though.

John

[ithacaartist]

Wouldn't the re-curve of the sear spring increase trigger pull?

[JohnW...ski]

Originally Posted by ithacaartist

Wouldn't the re-curve of the sear spring increase trigger pull?

It probably did, but the next time I checked it it had returned nearly to its original curve, however, the doubling had not come back.

John